Small diameter embolic coil hydraulic deployment system

ABSTRACT

A medical device for placing a very small embolic coil at a preselected location within a vessel comprising a positioning catheter having a distal tip for retaining a headpiece with an attached embolic coil such that when the catheter is pressurized with a fluid the distal tip of the catheter expands outwardly to release the headpiece and coil at the preselected position.

This application is a continuation of U.S. application Ser. No.09/177,848, filed Oct. 22, 1998 now U.S. Pat. No. 6,113,622.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a medical device for placing an emboliccoil at a preselected location within a vessel of the human body, andmore particularly, relates to a very small diameter catheter having adistal tip for retaining an embolic coil in order to transport the coilto a preselected position within the vessel and a control mechanism forreleasing the embolic coil at the preselected position. This device isparticularly suited to transport an embolic coil through the tortuousvasculature of the human brain.

2. Description of the Prior Art

For many years flexible catheters have been used to place variousdevices within the vessels of the human body. Such devices includedilatation balloons, radiopaque fluids, liquid medications and varioustypes of occlusion devices such as balloons and embolic coils. Examplesof such catheter devices are disclosed in U.S. Pat. No. 5,108,407,entitled “Method And Apparatus For Placement Of An Embolic Coil”; U.S.Pat. No. 5,122,136, entitled, “Endovascular Electrolytically DetachableGuidewire Tip For The Electroformation Of Thrombus In Arteries, Veins,Aneurysms, Vascular Malformations And Arteriovenous Fistulas.” Thesepatents disclose devices for delivering embolic coils to preselectedpositions within vessels of the human body in order to treat aneurysms,or alternatively, to occlude blood vessels at a particular location.

Coils which are placed in vessels may take the form of helically woundcoils, or alternatively, may be random wound coils, coils wound withincoils or many other such coil configurations. Examples of various coilconfigurations are disclosed in U.S. Pat. No. 5,334,210, entitled,“Vascular Occlusion Assembly; U.S. Pat. No. 5,382,259, entitled,“Vasoocclusion Coil With Attached Tubular Woven Or Braided FibrousCovering.” Embolic coils are generally formed of a radiopaque metallicmaterials, such as platinum, gold, tungsten or alloys of these metals.Often times several coils are placed at a given location in order toocclude the flow of blood through the vessel by promoting thrombusformation at the particular location.

In the past, embolic coils have been placed within the distal end of thecatheter. When the distal end of the catheter is properly positioned thecoil may then be pushed out of the end of the catheter with a guidewirein order to release the coil at the desired location. This procedure ofplacement of the embolic coil is conducted under fluoroscopicvisualization such that the movement of the coil through the vasculatureof the body may be monitored and the coil may be placed in the desiredlocation. With these placements systems there is very little controlover the exact placement of the coil since the coil may be ejected to aposition some distance beyond the end of the catheter. As is apparent,with these latter systems, when the coil has been released from thecatheter it is difficult, if not impossible, to retrieve the coil or toreposition the coil.

Numerous procedures have been developed to enable more accuratepositioning of coils within a vessel. Still another such procedureinvolves the use of a glue or solder for attaching the embolic coil to aguidewire, which is in turn, placed within a flexible catheter forpositioning the coil within the vessel at a preselected position. Oncethe coil is at the desired position, the coil is held in position by thecatheter and the guidewire is pulled from the proximal end of thecatheter to thereby cause the coil to become detached from the guidewireand released from the catheter. Such a coil positioning system isdisclosed in U.S. Pat. No. 5,263,964, entitled, “Coaxial TractionDetachment Apparatus And Method.”

Another coil positioning system utilizes a catheter having a socket atthe distal end of the catheter for retaining a ball which is bonded tothe proximal end of the coil. The ball, which is larger in diameter thanthe outside diameter of the coil, is placed in a socket within the lumenat the distal end of the catheter and the catheter is then moved into avessel in order to place the coil at a desired position. Once theposition is reached, a pusher wire with a piston at the end thereof ispushed distally from the proximal end of the catheter to thereby pushthe ball out of the socket in order to thereby release the coil at thedesired position. Such a system is disclosed in U.S. Pat. No. 5,350,397,entitled, “Axially Detachable Embolic Coil Assembly.” One problem withthis type of coil placement system which utilizes a pusher wire whichextends through the entire length of the catheter and which issufficiently stiff to push an attachment ball out of engagement with thesocket at the distal end of the catheter is that the pusher wireinherently causes the catheter to be too stiff with the result that itis very difficult to guide the catheter through the vasculature of thebody.

Another method for placing an embolic coil is that of utilizing a heatreleasable adhesive bond for retaining the coil at the distal end of thecatheter. One such system uses laser energy which is transmitted througha fiber optic cable in order to apply heat to the adhesive bond in orderto release the coil from the end of the catheter. Such a method isdisclosed in U.S. Pat. No. 5,108,407, entitled, “Method And ApparatusFor Placement Of An Embolic Coil.” Such a system also suffers from theproblem of having a separate fiber optic element which extendsthroughout the length of the catheter with resulting stiffness to thecatheter.

Still another coil deployment system incorporates a catheter having alumen throughout the length of the catheter and a distal tip forretaining the coil for positioning the coil at a preselected site. Thedistal tip of the catheter is formed of a material which exhibits thecharacteristic that when the lumen of the catheter is pressurized thedistal tip radially expands to release the coil at the preselected site.Such a deployment system is disclosed in the parent patent application,U.S. patent No. application Ser. No. 09/177,848, filed on Oct. 22, 1998,and entitled, “Embolic Coil Hydraulic Deployment System,” assigned tothe assignee of the present patent application.

SUMMARY OF THE INVENTION

The present invention is directed toward a very small diameter vascularocclusive coil deployment system for use in placing an embolic coil at apreselected site within a vessel which includes a small diameter,flexible catheter having a distal tip for retaining the coil so that thecoil may be moved to the preselected site within the vessel. Thecatheter has a lumen which extends therethrough the length of thecatheter and also includes a distal end which is formed of a materialhaving a durometer such that when a fluid pressure of about 300 poundsper square inch (psi) is applied to the interior of the catheter, thewalls of the distal tip expand outwardly, or radially, to therebyincrease the lumen of the distal tip of the catheter. The embolic coilis disposed upon and bonded to a cylindrical headpiece which has adiameter approximately equal to the diameter of the lumen of thecatheter. The headpiece extends outwardly from the proximal end of thecoil and this portion of the headpiece is disposed within and retainedby the lumen at the distal tip of the catheter. A hydraulic injector,such as a syringe, is coupled to the proximal end of the catheter forapplying a fluid pressure to the lumen of the catheter. When the coil isplaced at a desired position within a vessel, fluid pressure is appliedto the lumen of the catheter by the hydraulic injector to thereby causethe walls of the distal tip to expand outwardly, or radially, to releasethe headpiece which carries with it the coil. Most importantly, thediameter of the headpiece is approximately equal to or slightly larger,than the diameter of the lumen of the catheter so that when theheadpiece 122 is inserted into the distal section of the catheter, theoutside diameter of the attached coil 106 is approximately equal to theoutside diameter of the catheter. This construction results in adeployment system having an overall outside diameter approximately equalto that of the catheter.

In accordance with another aspect of the present invention, the flexiblecatheter is comprised of a proximal section and a relatively shortdistal section. The proximal section is formed of a material which issufficiently flexible to be passed through the vasculature of the humanbody and is of a durometer which essentially resists outward expansionwhen a fluid pressure on the order of about 300 psi is applied to theinterior of the catheter. The distal section of the catheter is formedof a material which is also sufficiently flexible to be passed throughthe vasculature of the body, yet is of a durometer which issignificantly lower than the durometer of the proximal section andexhibits the property of expanding outwardly, or radially, when such afluid pressure is applied to the interior of the catheter to therebypermit the release of the headpiece to thereby release the embolic coil.

In accordance with still another aspect of the present invention, thedistal section of the catheter has a durometer in a range of betweenabout 25D and 55D.

In still another aspect of the present invention, the embolic coil iscomprised of a helical coil having a proximal end, a distal end, and alumen extending therethrough. A headpiece is partially disposed withinthe lumen of the proximal end of the coil and the other portion of theheadpiece is placed in fluid-tight engagement with the lumen of thecatheter.

In another aspect of the present invention, the hydraulic injector forapplying a fluid pressure to the interior of the catheter takes the formof a syringe which is coupled to the proximal end of the catheter for,upon movement of the piston, creating a fluid pressure which is appliedto the interior of the catheter to thereby cause the release of theembolic coil.

In accordance with another aspect of the present invention, the emboliccoil may take the form of other types of implantable devices, such as avascular filter.

These aspects of the invention and the advantages thereof will be moreclearly understood from the following description and drawings of apreferred embodiment of the present invention:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged, partial sectional view of the hydraulic vascularocclusive coil deployment system of the present invention;

FIG. 2 is an enlarged partially sectional view showing the distal end ofthe coil deployment system prior to deployment of the coil;

FIGS. 3 and 4 illustrate the sequential steps in the radial expansion ofthe distal tip of the coil deployment system as the embolic coil isreleased; and,

FIG. 5 illustrates the distal tip of the coil deployment system afterrelease of the embolic coil.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 generally illustrates the vascular occlusive coil deploymentsystem 100 which is comprised of a hydraulic injector or syringe 102,coupled to the proximal end of a catheter 104. An embolic coil 106includes a proximal headpiece 122 which is disposed within the lumen ofthe distal end 108 of the catheter. The headpiece 122 is tightly heldwithin the lumen of the distal section 108 of the catheter 104 until thedeployment system is activated for release of the coil. As may be seen,the syringe 102 includes a threaded piston 110 which is controlled by ahandle 112 for infusing fluid into the interior of the catheter 104.Also as illustrated, the catheter 104 includes a winged hub 114 whichaides in the insertion of the catheter into the vascular system of thebody.

FIG. 2 illustrates in more detail the distal end of the catheter 104.The catheter 104 includes a proximal section 116 and the distal section108. The embolic coil 106 is tightly wrapped and bonded to the distalportion of a cylindrical headpiece 122. The proximal portion of theheadpiece 122 is disposed within the distal section 108 of the catheterand is tightly held within the lumen 120 of this distal section 108prior to release of the headpiece 122 and attached coil 106. As may beappreciated, FIG. 2 illustrates the vascular occlusive coil deploymentsystem prior to activation of the piston of the syringe and prior torelease of the coil.

The embolic coil 106 may take various forms and configurations and mayeven take the form of a randomly wound coil, however, with the helicalwound coil as illustrated in FIG. 2, the coil is provided with aheadpiece 122 having a proximal portion which is disposed in a lumen 120which lumen extends throughout the length of the coil 106. The headpiece122 serves to retain the coil 106 and also to prevent the flow of fluidthrough the lumen of the coil 106. When the headpiece 122 is placed influid-tight engagement with the lumen 120 the headpiece serves toprovide a fluid-tight seal at the distal end of the catheter 104.Adjacent turns of the coil 106 at the proximal end 118 of the coil arepreferably continuously welded together and are in turn welded to theheadpiece 122 to provide a generally unitary structure. Mostimportantly, the diameter of the headpiece is approximately equal to orslightly larger, than the diameter of the lumen of the catheter so thatwhen the headpiece 122 is inserted into the distal section of thecatheter, the outside diameter of the attached coil 106 is approximatelyequal to the outside diameter of the catheter. This construction resultsin a deployment system having an overall outside diameter approximatelyequal to that of the catheter.

Preferably, the proximal section 116 and the distal section 108 of thecatheter 104 are formed of materials having different durometers. Theproximal section 116 is preferably formed of Pebax material having adurometer in a range of about 62D to 75D. The proximal section issufficiently flexible to transverse the vasculature of the human body,but is sufficiently rigid such that when a fluid pressure ofapproximately 300 psi is applied to the interior of this section of thecatheter there is very little, if any, radial expansion of the walls ofthis section. On the other hand, the distal section 108 of the catheteris preferably formed of polymer material with a relatively low durometerwhich, exhibits the characteristic that when a fluid pressure ofapproximately 300 psi is applied to the interior of the catheter thewalls of the distal section 108 expand radially, somewhat similar to theaction of a balloon inflating, to thereby release the proximal end 118of the coil 106. As may be appreciated, there are numerous materialswhich could be used to fabricate the proximal section 116 and distalsection 108 of the catheter 104, however, the distal section 108 ispreferably formed from a block copolymer such as Pebax having adurometer of between 25D and 55D with a durometer of 40D being thepreferred durometer.

FIGS. 3 and 4 generally illustrate the coil release mechanism in actionfor the vascular occlusive catheter deployment system. Moreparticularly, as shown in FIG. 3, when a hydraulic pressure is appliedto the interior 124 of the catheter 104 the relatively low durometerdistal section 108 of the catheter begins to expand radially, much as aballoon expands during the process of inflation. As the distal section108 continues to expand radially there comes a point as illustrated inFIG. 4 in which the headpiece 122 and attached coil 106 becomesdisengaged from the lumen of the distal section 108 and the coil is thenreleased from the catheter and is deployed within the vessel.

As illustrated in FIG. 5, when the headpiece 122 and the coil 106 havebeen released from the catheter 104, the catheter may then be withdrawnleaving the coil positioned at the desired site.

With the vascular occlusive coil deployment system of the presentinvention it is possible to place an embolic coil very precisely at adesired location within a vessel. Once the coil has been placed in thatlocation by use of the catheter, the catheter may be activated byapplying a hydraulic pressure to the interior of the catheter to therebycause the catheter to release the coil and deposit the coil veryaccurately at the desired location.

As is apparent, there are numerous modifications of the preferredembodiment described above which will be readily apparent to one skilledin the art, such as many variations and modifications of the coilincluding numerous coil winding configurations, or alternatively othertypes of implant devices, such as a vascular filter. Also, there areobviously variations of the syringe arrangement for applying a fluidpressure to the interior of the catheter, including many other fluidpressure generating systems for increasing the pressure within theinterior of a catheter in order to cause the distal section of thecatheter to expand. These modifications would be apparent to thosehaving ordinary skill in the art to which this invention relates and areintended to be within the scope of the claims which follow.

That which is claimed is:
 1. A small diameter vasocclusive coildeployment system for use in placing a coil at a preselected site withina vessel comprising: an elongated flexible catheter having a lumenextending therethrough so as to define an outer wall and having aproximal sect ion and a distal section, said distal section of thecatheter being formed of a material having a durometer which exhibitsthe characteristic that when a fluid pressure is applied to the lumen ofthe catheter the outer wall of the distal section of the catheter iscaused to expand outwardly; an embolic coil assembly comprised of ahelically wound flexible coil having proximal and distal ends and acylindrical headpiece having proximal and distal sections, the distalsection of the headpiece is disposed within the proximal end of thehelically wound coil and the proximal section of the headpiece extendsoutwardly beyond the proximal end of the helically wound coil, saidproximal section of the cylindrical headpiece having a diameterapproximately equal to the diameter of the lumen of the catheter andsaid proximal section of said cylindrical headpiece being disposed influid-tight engagement within the lumen of the distal section of thecatheter; and, a syringe coupled to the proximal section of the catheterfor applying a fluid pressure to the interior of the catheter to therebycause the distal section of the catheter to expand outwardly to therebyrelease the cylindrical headpiece to thereby deploy the embolic coilassembly.
 2. A vasoocclusive coil deployment system as defined in claim1, wherein said proximal section of said catheter is formed of amaterial which is sufficiently flexible to be passed through thevasculature of the body and is formed of a material which exhibits thecharacteristic of having substantially no radial expansion when a fluidpressure of about 300 psi is applied to the lumen of the proximalsection of the catheter, the distal section is formed of a materialwhich is also sufficiently flexible to be passed through the vasculatureof the body and is of a durometer which is substantially lower than thedurometer of the proximal section.
 3. A vasoocclusive coil deploymentsystem as defined in claim 1, wherein the helically wound coil has anoutside diameter which is approximately equal to an outside diameter ofthe catheter to thereby provide a coil deployment system of a uniformoutside diameter.
 4. A vasoocclusive coil deployment system as definedin claim 3, wherein the distal section of the catheter is formed of apolymer having a durometer in a range of between 25D and 55D.
 5. Avasoocclusive coil deployment system as defined in claim 3, wherein thedistal section of the catheter is formed of a polymer having a durometerof about 45D.
 6. A small diameter vasoocclusive coil deployment systemfor use in placing a coil at a preselected site within a vesselcomprising: an elongated flexible catheter having a lumen extendingtherethrough so as to define an outer wall and having a proximal sectionand a distal section, said distal section of the catheter being formedof a material having a durometer which exhibits the characteristic thatwhen a fluid pressure is applied to the lumen of the catheter the outerwall of the distal section of the catheter is caused to expandoutwardly; an embolic coil assembly comprised of a flexible coil havingproximal and distal ends and a cylindrical headpiece having proximal anddistal sections, the distal section of the headpiece is disposed withinthe proximal end of the coil and the proximal section of the headpieceextends outwardly beyond the proximal end of the coil, said proximalsection of the cylindrical headpiece having a diameter approximatelyequal to the diameter of the lumen of the catheter and said proximalsection of said cylindrical headpiece being disposed in fluid-tightengagement within the lumen of the distal section of the catheter; and,a connector coupled to the proximal section of the catheter and adaptedfor coupling a source of fluid pressure to the interior of the catheterto thereby cause the distal section of the catheter to expand outwardlyto thereby release the cylindrical headpiece to thereby deploy theembolic coil assembly.
 7. A vasoocclusive coil deployment system asdefined in claim 6, wherein said proximal section of said catheter isformed of a material which is sufficiently flexible to be passed throughthe vasculature of the body and is formed of a material which exhibitsthe characteristic of having substantially no radial expansion when afluid pressure of about 300 psi is applied to the lumen of the proximalsection of the catheter, the distal section is formed of a materialwhich is also sufficiently flexible to be passed through the vasculatureof the body and is of a durometer which is substantially lower than thedurometer of the proximal section.
 8. A vasoocclusive coil deploymentsystem as defined in claim 6, wherein the coil has an outside diameterwhich is approximately equal to an outside diameter of the catheter tothereby provide a coil deployment system of a uniform outside diameter.9. A small diameter vasocclusive medical device deployment system foruse in placing a medical device at a preselected site within a vesselcomprising: an elongated flexible catheter having a lumen extendingtherethrough so as to define an outer wall and having a proximal sectionand a distal section, said distal section of the catheter being formedof a material having a durometer which exhibits the characteristic thatwhen a fluid pressure is applied to the interior of the catheter thewalls of the distal section of the catheter expand outwardly; a medicaldevice assembly comprised of a medical device having proximal and distalends and a cylindrical headpiece having proximal and distal sections,the distal section of the headpiece is coupled to the proximal end ofthe medical device and the proximal section of the headpiece extendsoutwardly beyond the proximal end of the medical device, said proximalsection of the cylindrical headpiece having a diameter approximatelyequal to the diameter of the lumen of the catheter and said proximalsection of said cylindrical headpiece bring disposed in fluid-tightengagement with the lumen of the distal section of the catheter; and, aconnector coupled to the proximal section of the catheter and adaptedfor coupling a source of fluid pressure to the interior of the catheterto thereby cause the distal section of the catheter to expand outwardlyto thereby release the cylindrical headpiece with the medical, device.10. A vasoocclusive medical device deployment system as defined in claim9, wherein said proximal section of said catheter is formed of amaterial which is sufficiently flexible to be passed through thevasculature of the body and is formed of a material which exhibits thecharacteristic of having substantially no radial expansion when a fluidpressure of about 300 psi is applied to the lumen of proximal section ofthe catheter, the distal section is formed of a material which is alsosufficiently flexible to be passed through the vasculature of the bodyand is of a durometer which is substantially lower than the durometer ofthe proximal section.
 11. A vasoocclusive medical device deploymentsystem as defined in claim 9, wherein the Medical device has an outsidediameter which is approximately equal to the outside diameter of thecatheter to thereby provide a medical device deployment system of auniform outside diameter.
 12. A small diameter vasocclusive coildeployment system for use in placing a coil at a preselected site withina vessel comprising: an elongated flexible catheter having a lumenextending therethrough so as to define an outer wall and having aproximal section and a distal section, said distal section of thecatheter being formed of a material having a durometer which exhibitsthe characteristic that when a fluid pressure generating device isapplied to the lumen of the catheter the outer wall of the distalsection of the catheter is caused to expand outwardly; an embolic coilassembly comprised of a helically wound flexible coil having proximaland distal ends and a cylindrical headpiece having proximal and distalsections, the distal section of the headpiece is disposed within theproximal end of the coil and the proximal section of the headpieceextends outwardly beyond the proximal end of the coil, said proximalsection of the cylindrical headpiece having a diameter approximatelyequal to the diameter of the lumen of the catheter and said proximalsection of said cylindrical headpiece being disposed in fluid-tightengagement with the lumen of the distal section of the catheter; and, asource of fluid pressure coupled to the proximal section of the catheterfor applying a fluid pressure to the interior of the catheter to therebycause the distal section of the catheter to expand outwardly to therebyrelease the cylindrical headpiece to thereby deploy the embolic coilassembly.
 13. A vasoocclusive coil deployment system as defined in claim12, wherein said proximal section of said catheter is formed of amaterial which is sufficiently flexible to be passed through thevasculature of the body and is formed of a material which exhibits thecharacteristic of having substantially no radial expansion when a fluidpressure of about 300 psi is applied to the lumen of the proximalsection of the catheter, the distal section is formed of a materialwhich is also sufficiently flexible to be passed through the vasculatureof the body and is of a durometer which is substantially lower than thedurometer of the proximal section.
 14. A vasoocclusive coil deploymentsystem as defined in claim 12, wherein the helically wound coil has anoutside diameter which is approximately equal to an outside diameter ofthe catheter to thereby provide a coil deployment system of a uniformoutside diameter.